Depletion of fossil fuels has brought about a great increase in price of energy sources and increased interest in environmental pollution. Eco-friendly alternative energy sources are a necessity for the next generation. In this regard, a great deal of research into power production methods such as nuclear energy and sunlight, wind power and tidal power is underway and power storage devices for efficiently utilizing the produced energy are also attracting much attention.
In particular, regarding lithium secondary batteries, an increase in technological development and demand associated with mobile equipment has led to a sharp increase in demand for lithium secondary batteries as energy sources. Recently, use of lithium secondary batteries as power sources of electric vehicles (EVs) and hybrid electric vehicles (HEVs) has become popular and usage thereof is expanding to applications such as auxiliary power supply through grid-implementation.
A conventional lithium secondary battery generally utilizes a lithium metal composite oxide for a cathode and a graphite-based compound for an anode. On the other hand, recently, rather than conventional carbon-based anode materials, a great deal of research associated with anode materials obtained through lithium alloy reactions using silicon (Si) and tin (Sn), and lithium titanium oxides is underway.
Lithium titanium oxide is known as a zero-strain material that suffers minimal structural deformation during charge/discharge, exhibits considerably superior lifespan, does not cause generation of dendrites and has considerably superior safety and stability.
However, lithium titanium oxide has a limitation of insufficient capacity as compared to conventional carbon-based anode materials, although it has a theoretical capacity of 175 mAh/g and an improved capacity to a level of 160 to 170 mAh/g to date.
Accordingly, there is an increasing need for methods capable of improving performance of secondary batteries by providing desired capacity, power and safety, in spite of using lithium titanium oxide as an anode active material.